The present invention relates to a plastic fastener and a method of fastening components components.
A conventional vehicular generator, sometimes referred to as an alternator, includes a variety of electrical components, such as a positive heat sink, a rectifier bridge, a brush box, and a voltage regulator. These components are commonly secured to each other and/or to the generator frame. Mounting the components in this fashion enhances heat transfer within the generator, secures the electrical components so as to reduce damaging vibrations, and may provide electrical grounds and positive electrical connections between various components.
The electrical components are commonly mounted with threaded fasteners, such as screws. However in order to maintain electrical isolation between the fastener, components, and frame, plastic or other insulators are typically required. Such an approach is shown in U.S. Pat. No. 6,304,012 to Chen et al., which depicts a mounting bolt (255) having an insulator (256) for insulating the slip ring end housing (74) from the rectifier (252). A similar approach is also shown in U.S. Pat. No. 5,712,517 to Schmidt et al., which illustrates rivets (75) with rivet insulators (76) that are used to secure an interconnection plate (70) to an upper surface (9) of a control plate/heat sink (10).
Nevertheless, the typical method of securing generator components with insulated threaded fasteners presents several challenges. To avoid loosening of the fastener, the fastener must be maintained at a high tension. This tension results in a continuously high compressive load on the plastic insulator at high temperatures. Under such a load, the plastic insulator may creep, and loosen the fastener. Loose fasteners may lead to a lower compressive load on the components in the stack-up, which may deteriorate the necessary electrical contact between the components.
There is consequently a need in the art for a vehicular generator fastener, and/or a method of fastening components of a vehicular generator, that overcomes one or more of the above limitations.
One object of the present invention is to provide a solution to one or more problems set forth above. One advantage of the present invention is that a plastic fastener, as disclosed herein, replaces more expensive steel screws and related accessories, such as compression limiters, and/or spring elements like crest-cup washers. Since the present invention serves as both a fastener and an insulator, it more efficiently utilizes available package space where the accommodation of both metal fasteners and necessary insulation may be required. In addition, as the plastic fastener is an electrical insulator, the inventive fastener reduces local grounding of the components, such as salt bridging. Moreover, because the plastic fastener is more flexible than a metal screw, greater tolerances may be designed in the stack up of mating components; that is, the mounting aperture of a first component need not align exactly with the mounting aperture of a second component.
It is a primary object of the present invention to overcome the foregoing problems and/or to satisfy at least one of the aforementioned needs. The invention provides a plastic fastener for a vehicular generator having a body that extends through an aperture of a first component of the generator and that extends through an aperture of a second component of the generator. The plastic body has a first distal head that retainingly abuts an outer opening of the aperture of the first component. The plastic body also has a second distal head that retainingly abuts an outer opening of the aperture of the second component. The configuration of the plastic body secures the first component to the second component.
The invention further provides a method of fastening components of a vehicular generator. A first component of the generator is provided. The first component has an aperture. A plastic body is extended through the aperture of the first component. The plastic body has a first stud end and a second stud end. The second stud end is extended through an aperture of a second component of the generator. The first stud is then formed into a first distal head that retainingly abuts an outer opening of the aperture of the first component. The second stud is formed into a second distal head that retainingly abuts an outer opening of the aperture of the second component. This method secures the first component to the second component.